The proposed projects will be part of a long-range program, now in progress, on the anatomy of cortical and subcortical visual centers in Primates. The goals of the projects are to provide detailed information on the mode of termination of afferent systems to area 17 in squirrel monkey. Major efforts will be undertaken to reveal the recipient cell type(s) of specific afferents to layers IV and VI. Attention will focus on chemospecificty (GABA) of neurons in these layers. The methods applied during the course of the work are the degeneration technique, the Golgi silver impregnation, intracortical injection of GABA and its uptake, and finally reconstruction of neurons from ultrathin serial sections and overlapping photography. Whenever possible, efforts will be made to quantify the results.